Solid propellent compositions and a process for their preparation



f-so Io PROPELLENT COMPOSITIONS AND A l PROCESS non THEIR PREPARATION E. Malian and William M. Hutchinson, Bartlesville,

-.0kla., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Jam-27, 1956, Ser.No. 561,944

6 Claims. c1. sz--,.5

This invention relates to "improved solid propellent compositions and to a method for their preparation. In one of its aspects, this invention relates'to novel solid propellent compositions having improvedproperties comprising an oxidant, a polymeric material and compounding ingredients therefor, and a burning catalyst.

Recently, it has been discovered that superior solid 2,941,878 Patented June 21, 1960 ice j 2 and a binder comprising a rubbery copolymer of a conjugated diene and a heterocyclic nitrogen base can beimproved in the properties of elongation and modulus of elasticity without a sacrifice of the property of tensile strength by incorporation therein, prior tocuring, ,of-a minor amount of ammonium dichromate or acomplex metal cyanide such as milori blue, Prussian blue or Tux-n bulls blue. The specific beneficial results are obtained propellent materials are obtained comprising a solid oxidant such as ammonium nitrate or ammonium perchlorate, and a rubbery material such as a copolymer of butadiene and a vinylpyridine orother substituted heterocyclic nitrogen base compound, which after incorporation'is cured by a quaternization reaction or a vulcanization reaction. Solid propellent mixtures of this nature and a process for their production are disclosed and claimed in copending application Serial No. 284,447, filed April 25,1952, by W. B. Reynolds and I. E. Pritchard.

In the production of such solidpropellent compositions, it is desirable that the products have good mechanieal properties such as high elongation, low modulus, and high tensile strength as well as good burning rate.

It is an object of this invention to provide solid propellent compositions having-a high value of elongation. lt isialso an object of this invention to provide solid propellent compositions having a low modulus of elasticity.

"It -is' alsoan object-of this invention to provide a solid propellent composition having high tensile strength. It is 'a-further object of this-invention to provide a method for the production of solid propellent compositions having the above referred to properties of high elongation, low modulus of elasticity, and high tensile strength and also improved burning rate characteristics. It is 'an object to provide an improvement in properties of elongation and modulus in a propellent composition without sacrifice of properties of tensile strength; Other objects and advantages will be apparent to one skilled in this art upon studyof the disclosure of this invention.

Broadly, the invention contemplates the preparation'of a solid propellent composition comprising a solid oxidant and a binder comprising a rubbery copolymer of a conjugated diene and a heterocyclic nitrogen base and a minor portion of ammonium dichromate or a complex metal cyanide.

We have discovered that the addition of a minor portion of a complex metal cyanide or of'arnmonium dichromate to a propellent composition comprising a solid oxidant and a binder of a rubbery copolymer of a congroup. That is, the substituent is either. a vinyl or'an alpha-methylvinyl .(isopropenyl) group. Of these, the

jugated diene and a heterocyclic nitrogen base imparts a tions comprising an ammonium nitrate-containing oxidant diene'and contain one, and only one,

when the oxidant contains ammonium nitrate in an amount in excess of about 15 weight percent of the tota l oxidant. f

The rubbery polymers employed as binders in the solid propellent compositions of this invention-arecopol'ymers of conjugated dienes with polymerizable heterocyclic nitrogen bases of the pyridine series. These copolymers can vary inconsistency from very soft rubbers, i.e., -materials which are soft at room temperature but will show retraction when relaxed, to those having a Mooney value (ML-4) up to 100. The rubbery copolymers most frequently preferred have Mooney values in the range between 10 and 40. They may be prepared by any polymerization methods known to the art, e.g., mass or emulsion polymerization. One convenient method for pre-g paring these copolymers is by emulsion polymerization at temperatures in the range between 0 and 1140" F. Recipes such as the iron pyrophosphate-hydroperoxide, either sugar-free or containing sugar, the sulfoxylate, and the persulfaterecipes are among those which are appli cable. It is advantageous to polymerize to high conversion as the unreacted vinylpyridine monomer is difircult .to remove by stripping.

The conjugated dienes employed are those containing from 4 to 6 carbon atoms per molecule and include 1,3- butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl- 1,3-butadiene, and the like. Various alkoxyfs uch as methoxy and ethoxy and cyano derivatives of these conjugated dienes, are also applicable. Thus, other dienes", such. as phenylbutadiene, 2,3-dirriethyl-1,3-hexadiene, 2- methoxy-3-ethylbutadiene, 2-ethoxy-3 ethyl 1,3 hexadiene, 2-cyano-l,3-butadiene, are also applicable in the preparation of the polymeric binders of'this invention. Insteadof using a single conjugated diene, air mixture of conjugated dienes can befemployed. Thus, 35min ture of 1,3-butadieneand isoprene can beemployed as the conjugated diene portion of the monomer system l-f The polymerizable heterocyclic nitrogen basesfwhich are applicable for the production of the polymeric materials are those of the pyridine, quinoline,and isoquinoline series which'are copolymerizable with a conjugated substituent wherein R is either hydrogen or a methyl where the alkylsubstituents are methyl and/or ethyl are available commercially;

mixture of oxidant and binder.

These heterocyclic nitrogen bases have theformula R where R is selected from the group consisting ofhydrogen, alkyl, vinyl, alpha-methylvinyl, alkoxy, halo, hydroxy, cyano, aryloxy, aryl, and combinations of these groups such as haloalk yl, alkylaryl, hyroxyaryl, and the likej gadgets one and only one of said groups being selected from the group consisting of vinyl and alpha-methylvinyl; and the total number of carbon atoms in the nuclear substituted groups being not greater than 15. Examples of such compounds are 2 -vinylpyridine; 2-vinyl-5-ethylpy ridine; Z-methyl-S-vinylpyridine; 4-vinylpyridine; 2,3,4-trimethyl-S-vinylpyridine; 3,4,S,6-tetramethyl 2 vinylpyridine; 3-ethyl-5-vinylpyridine; 2,6-diethyl-4-vinylpyridine; 2 -isopropyl-4-nonyl-S-vinylpyridine; '2methy1-5 undecyl- 3-vinylpyridine; 2,4-dimethyl-5,6-dipentyl-3-vinylpyridine;

Z-decyi-S-(alpha-methylvinyl)pyridine; 2-vinyl-3 methyl- S-ethylpyfidine; 2-methoxy-4-chloro 6 vinylpyridine; 3- VinyI-Sethoxypyridine; 2- vinyl 4,5-dichloropyridine; 2- '(alpha-methylvinyl)-4-hydroxy-6-cyanopyridine; 2-vinyl- 4=phenoxy-S-methylpyridine; 2 cyano S-(alpha-methylvinyl)pyridine; 3-vinyl-5-phenylpyridine; Z-(para-methylphenyl) -3-vinyl-4-methylpyridine; 3-vinyl-5 (hydroxyphenyl)-pyridine; 2-vinylquinoline; 2-vinyl-4 ethylquinoline; 3-vinyl-6,7-di-n propylquinoline; 2-methyl-4 nonyl- G-vinylquinoline; 4(alpha-methylvinyl) -8 dodecylquinoline; 3-vinylisoquinoline; 1,6-dimethyl 3 vinylisoquinoline; 2-vinyl-4-benzylquinoline; 3-vinyl 5 chloroethyl quinoline; 3-vinyl-5,6 -dichloroisoquinoline; 2 vinyl 6'- ethoxy-7-methylquinoline; 3-vinyl 6 hydroxymethyliso- 'quinoline; and the like.

" Oxidants which are applicable in the solid propellent compositions of this invention include ammonium, alkali 'metal, and alkaline earth metal salts of nitric, perchloric,

and chloric acids, and mixtures thereof. Ammonium nitrate and ammonium perchlorate are the preferred oxidantsfo'r use in the solid rocket fuels of this invention. Specific oxidants include sodium nitrate, potassium perchlorate, lithium chlorate, calcium nitrate, barium perchlorate, and strontium chlorate. Mixtures of oxidants are also applicable. In the preparation of the solid rocket propellent compositions, the oxidants are powdered to sizes preferably 300 to 10 microns average particle size. The amount of solid oxidant employed is usually a major amount of the total composition and is generally in. the range between 50 and '90 percent by weight of the'total If desired, however-Jess I than 50 percent by weight of the oxidant can be used.

Combustion rate catalysts applicable in the invention include ammonium dichrornate and metal ferrocyanides and ferricyanides. Ferric ferrocyanides, such as Prussian,

.4 parts of rubbery'polymer with from 5 to 50 parts being most frequently preferred. The amount of combustion catalyst will usually be 0.25 to 12 parts by weight per hundred parts of oxidant and binder.

The binder contains a rubbery copolymer of the type hereinbefore described and, in addition, there may be present one or more reinforcing agents, plasticizers, wetting agents, and antioxidants. Other ingredients which are employed for sulfur vulcanization include a vulcanization accelerator, a vulcanizing agent such as sulfur, and an accelerator activator, such as zinc oxide.

The copolymer comprising a conjugated dieneand a polymerizable heterocyclic nitrogen basecan also be cured by a quaternization reaction by incorporating there; in a quaternizing agent and subjecting the resulting mixture to quaternizing'conditions of temperature, Suitable quaternizing agents include alkyl halides such as methyl iodide, methyl bromide; alkylene. halides. such; as methylene iodide, ethylene bromide; substituted alkane such as chloroform, bromoform; alkyl sulfates such as methyl sulfate; and various substituted aromatic compounds suchas benzoyl chloride, methyl benzenesulfonate, and the'like.

The. quaternizing temperature isusually in the range zero to 175 C.,'although temperatures outside this range can be used. i

A general formulation for a binder composition prepared by sulfur vulcanization is given below:

Parts by weight Rubbery copolymer (as hereinbefore described) 100 Reinforcing agent Plasticizer 0-100 Wetting agent 0-10 Antioxidant 0-3 vulcanization accelerator 0-5 Sulfur Q. O2 Zincoxide 0-5 A (amylbiphenyl), Paraflux (saturated polymerized hydrocarbon), Circosol-ZXH (petroleum hydrocarbon softener'having a. specific gravity of 0.940 and a Saybolt Universalviscosity. at 100 F. of about 2000 seconds), di(1,4,7 trioxaundecyl)methane, and dioctyl phthalate are suitable plasticizers. Materials which provide rubber having good low temperature properties arepreferred. It is also frequently preferred that the plasticizers bev oxygencontainingmaterials. V

Wetting. agents aid in defiocculating or dispersing the oxidizer, Aerosol OT (dioctyl ester of sodium sulfosuccinic acid)','lecithin, and Duomeen C diacetate (the Berlin, Hamburg, Chinese, Paris, and milori blue, soluble. ferric ferrocyanide, such as soluble Berlin or Prussian blue which contains potassium ferric ferrocyanide, and ferric ferrocyanide which'has been treated with ammonia, are-among the materials whichcan be used. .Ferrous ferricyanide, Turnbulls blue is also applicable. A-par which is pigment similar to Prussian blue but having a red tint and is prepared by the oxidation of a paste of potassium ferrocyanide and ferrous sulfate. Other metal ticularly effective burning rate catalyst is milori blue -bis(4-metl1yl 6-tertabutylphenol), and the like.

diacetate of trimethylenediamine substituted by a coconut oil product) are among the. materials which are applicable.

Antioxidants include Flexamine (physical mixture containing. 25. percentof a complex diarylamine-ketone reactionproduct and 35 percent of N,N'-diphenyl-p-phenylenediamine), phenyl-beta-naphthylamine, 2,2-methylene- Rubber antioxidants, 'in general, may be employed or if desired may be. omitted.

Examples of vulcanization accelerators are those of the carbamate type, such as N,N'-dimethylS-tert-butylsulfenyl dithiocarbamate and Butyl-Eight. Butyl Eight is a rubber accelerator of the dithiocarbamate type supplied by the R. F Vanderbilt Company and described in Handbook of Material Trade Names by Zimmerman and 1 Levine, 1953 Edition, as a brown liquid; specific gravity l '5 1.01; partially soluble-in water and gasoline; and soluble in acetone, alcohol, benzol, carbon disulfide and chloroform.

It is to be understood that each of the various types of compounding ingredients may be used singly or mixtures of various ingredients performing a certain function may be employed. It is sometimes preferred, for example to use mixtures of plasticizers rather than a single material.

fIhe various ingredients in the propellent composition may be mixed on a roll mill or an internal mixer such as a Banbury or a Baker-Perkins dispersion blade mixer may be employed. The binder forms a continuous phase in the propellent with the oxidant as the discontinuous phase.

' Rocket grains are formed by compression molding, in-

v jection molding, or extrusion.

' The curing time must be long enough to give required creep resistance and other mechanical propertiesin the propellant. The timev will generally range from around three hours when the higher curing temperatures are employed to seven days when curing is effected at lower temperatures.

While this invention has been described using as the binder for propellent compositions a copolymer of a conjugated diene with a polymerizable heterocyclic nitrogen base of the pyridine series, such as vinylpyridine and various: alkyl-substituted derivatives, it is to be under- .stood that the corresponding quinoline and isoquinoline compounds are also applicable, i.e., vinylquinolines, vinyl- .isoquinolines and various alkyl-substituted derivatives of these compounds.

EXAMPLE I Two solid propellants were prepared having compositions as follows: v

/ Parts by Weight Oxidizer (NH NO 85 85 Binder .15 15 Milori blue 7 2 The binder composition was prepared using a 90/ 10 butadiene/Z-methyl-S-vinylpyridine copolymer having a Mooney value (ML-4) of 20. This composition was prepared in accordance with the following formulation:

Dioctyl ester of sodium sulfosuccinic acid.

Physical mixture containing 25 percent of a complex diarylamine-ketone reaction product and 35 percent of N,N-diphenyl-p-phenylenediamine.

The various ingredients making up the solid propellents were mixed in a Baker-Perkins dispersion blade mixer with the binder forming the continuous phase in the final composition. The material from each composition was extruded into strands di inches in diameter for ballistic test specimens and a sheet 0.25 inch in thickness from which tensile specimens were stamped out prior to curing. The specimens .were cured 24 hours at 170 F.

fland mechanical and ballistic proper-ties determined.v Results are reported in the following Table I.

. Table 1 [Mechanical properties at 70 F., 3 in./sec. Gross Arm speed. Ballistic properties at 70 F., 1000 p.s.i.]' I g Ultimate stress (tensile), p.s.i 335 2 64 Ultimate elongation, percent. 15. 8 3. 1 Modulus of elasticity, psi... 4, 400 10,000 Burning Rate, in./sec 0. 162 0. 100 n (pressure exponent) 0. 53 0. 65

1 n is defined by the formula L1 AP1 (1 1)? 1)" rfAPi W5" '""(1ooo r=rafe inJsee. at pressure P. P=pressure of chamber p.s.i.g. mnF-buming rate at the reference pressure of 1000 p.s.l.g.

EXAMPLE II Two solid propellants having the following composi tions were prepared: j

Parts by Weight Oxidizer (NH4NO3) 82.5 82.5

Binder 17. 5 17. 5

Milori blue 2 Ammonium diehrnmate 2 The binder was prepared usin'g'a 90/10 butadiene/2- methyI-S-VinyI-pyridine copolymer having a Mooney value (ML-4) of 20. This composition was prepared in accordance with the following formulation:

. H p Parts .by .weight Butadiene/2-methyl-S-vinylpyridine .copolyme'r' 100 v Carbon black 20 Benzophenone l0 'Pentaryl A 10 N,N-dimethyl-S-tert-butylsu1fenyldithiocar-bamate 1 Sulfur 0.75

40 Zinc oxide 3 Aerosol OT 1 p 7 ,1 Flexarnine 3 1 As in Example I. g j A Baker-Perkins dispersion blade mixer was employed for the mixing of various ingredients making up the solid propellent composition. The binder formed the continuous phase in the propellants. The material from each composition was extruded into strands i inch in diameter for ballistic test specimens and a sheet 0.25 inch in thickness from which tensile specimens were stamped. out prior to curing. The specimens were cured 24, hours at .170 F. and mechanical and ballistic properties, determined. The results are shown in Table II.

Table II [Mechanical properties at 70 F., 3 inJsee. cross arm speed. Ballistic properties at 70 F., 1000 p.s.i.]

Ultimate stress tensile .s.l

Ultimate elongaliomp rcgntfl Modulus of elasticity, p.s.i 4, 300 2, 945 Burning Rate, in./see 0.182 0.177 n (pressure exponent) 0. 50 0. 54

EXAMPLE III Two solid propellants having the following compositions were prepared:

Parts by Weight Oxidizer (N H NO The binder was prepared using a 90/10 butadiene/Z methyl-.i-vinylpyridine cepolyrner' in accordance with the following formulation: I

Parts by weight iBu-tadi ene/Z methyI S-VinylPyridine cop'olymer "1001 Qarbonblajck' 45;: 2 Be phen n Pentzrryl-Atamylbiphenyl) 10 Butyl-Eigh (diriqarbamate-type rubber accelerator 2. Sulfur I v ,7 1.75 Zinc oxide 3 Aerosol OT 1 1 Flexamine 1 n 3 1A8 in Example I. I a a Thev propellants were prepared as described in Examples I and II, and cured for 48 hours at 170? F. The results of testsare sho n n Ta le 1.

EXAMPLE Iv results of mechanicallproperties of Examples 1,

ILand'III are compared in the following tabulation:

I The binder formulations are not exactly 'the same in each caserb'ut the formulations are such as to provide a propellant in each case having an ultimate tensile strength in the range of '240 to 340 psi. These tests "demonstratethe advantages gained by the addition of milori blue or ammonium dichromate to the propellent formulation. In each case elongation values are higher and modulus values are lower than when rouge or no additive is used. 1 1

EXAMPLE V A solid propellant was prepared having the following composition:

a u 7 H Parts by weight Oxidizer (NH NO 8 Binder f Milori blue 2 The binder was prepared using a 90/10 butadiene/Z- methyl-S-vinylpyridine copolymer in accordance with the "following formulation:

' Parts by weight Butadiene/2=methyl-5-vinylpyridine copolymer 100 Carb n black Benzophenone 20 .Lauryl bromide amok 14 Flexamine 1 3 iAsinExample- I. V V K V The propellantwas prepared by thoroughly admixing the ingredients, shaping the mixture into the test pieces" T b 1V .i Catalystflparts .Tensile, Elonga Modulus,

- .Propellent by weight p.s.i. tion, p.s.i.

' percent 335- 15.8 4, 400 H r 3,1 10,000 Example 11. 349 19,. 5 4, 300 Example IL. 244 29. 5 2, 945 sample 111;--- Rouge 322 4.8 7,598 Example III"... 340 l8. 9 '1, 968

sear-gees aha Taming the specimens to: 24 hours at mm P. The "results oftests with Sin/min. cross-arm speed are-as follows:

Table V l l, V Tensile, Elongation, Modulus, Test Temperature, F. psi. percent psi.

example shows that desirable values of elongation and modulus are obtained when quaternization is used to cure the propellant EXAMPLE VI 7 Five solid propellants were prepared having compositions as follows:

Parts by weight oxidizer (NH4NO3) 82.5 Bind r 4 q x1745 Milori blue 0, 0.25, 0.5, l, 2

The binder composition was prepared using 'a' 90/10 butadiene/2-methyl-5winylpyridine copolymer having a Mooney value (ML-4) of 20. The formulation employed for preparationof this composition was the same as that given in Example II.

The various ingredients making up the solid propellants were mixed on a roll mill. Tensile specimens from each composition were compression molded and burning rate strands were extruded. All specimens were cured 24 hours at 170 F. Results of burning rate tests at 70 F.

and evaluation of mechanical properties on the propellants at 70? F. and 3 inilmin. cross arm speed are shown below:

The foregoing examples illustrate the unexpected improvement in the mechanical characteristics of the amffinonjium nitrate-containing propellent compositions wherein milori blue or ammonium dichrornate have been incorporated. Values of elongation are increased and values of modulus are decreased with no sacrifice of tensile strength values. It is noted that burning rate is progressively increased.

EXAMPLE VII Solid propellants were prepared similar to those-of the previous examples except that ammonium perchlorate was utilized as the oxidizer instead of ammonium nitrate.

The binder compositions were as follows:

Parts by Weight 1,3-Butadiene/Z-methyl-fi-vlnylpyridine copolymer 100 100 100 100 Carbon black 22 22 22 22 Butyl carbitol formal 20 20 20 20 N ,N-dlmethyl-S-tert-butylsulfenyl dithio- 'carbamate- 1 Sulfur V 0. Zinc oxide 3 1 M esium O i r 5 Flexamine 1 3 3 3 3 'Benzotrichloride 6 6 Propellent compositions were Ammonium perchlorate 85 85 85 Binder-(as above) 15 15 15 15 Milorl blue- 2 "2 Ammonium dichrnm'itn 4 garners Table VII [Mechanical properties at 70 F., 2 inJmin. cross-arm speed. Ballistic properties at 70 F., 1000 p.s.i.]

Ultimate stress (tensile), p.s.i 180 129 164 26 Ultimate elongation, percent... 15. 9 11. 3 9.1 46. 4 Modulus of elasticity, p.s.i. 1, 720 1, 850 2, 430 Vlery ow Burning rate, in./sec 2. 04 1. 12 1.23 0.75 as (pressure exponent) 0.51 0.45 0. 45 0.22

The results of Example VII demonstrate the efiect of incorporating a small amount ,of milori blue or ammonium dichromate in a solid propellent composition utilizing arm monium perchlorate as oxidant. The burning rate improvement is extremely high and provides a means for controlling the burning properties of a propellent composition.

Variations and modifications are possible within thescope of the disclosure of the present invention, the essence of which is the discovery that the addition of a minor amount of ammonium dichromate or a complex metal cyanide to a rocket propellent composition comprising a solid ammonium nitrate-containing oxidant, and a conjugated diene-heterocyclic nitrogen base copolymer provides an unexpected improvement in the mechanical characteristics of the propellant and in propellant compositions wherein ammonium nitrate is not employed in the oxidant a pronounced improvement in burning rate results from the presence of a minor amount of these materials.

That which is claimed is:

l. A propellant composition consisting essentially of an intimate admixture of from about 5-0 to about 90 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of an inorganic oxidizing salt and from about 10 to about 50 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of a binder selected from the'group consisting of a sulfur vulcanized copolymer and a quaternized copolymer of 1) a conjugated diene having up to 8 carbon atoms per molecule; (2) at least one CHF-O/ substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, alkyl substituted pyridine, and an alkyl substituted quinoline, wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of hydrogen and a methyl radical, to about 50 parts by weight per 100 parts of copolymer of carbon black, 0 to about 100 parts by weight per 100 parts of copolymer of a rubber plasticizer, 0 to about 10 parts by weight per 100 parts of copolymer of a wetting agent, 0 to about 3 parts by weight per 100 parts of copolymer of an antioxidant, and O to about parts by weight of 100 parts of copolymer of zinc oxide; and (3) about 0.25 to about 12 parts by weight per 100 parts of oxidizing salt and binder mixture of burning rate catalyst selected from the group consisting of ammonium dichromate and a complex cyanide of iron.

2. A composition of claim '1 wherein the inorganic oxidizing salt is ammonium nitrate; the conjugated diene is 1,3 butadiene; the heterocyclic nitrogen base is 2-methyl-5-vinylpyridine; and the burning rate catalyst milori blue.

3. The composition of claim 1 wherein the inorganic oxidizing salt is ammonium nitrate; the conjugated diene is 1,3 butaclieiiej the h terocyclie nitrogen base is Z-methyLS-VinyIpyridine; and the burning ratecatalyst is ammonium dichromate. r r

4. A propellant composition consisting essentially of from 50 to parts by weight per parts by weight of oxidizing salt and binder mixture of an inorganic oxidizing salt; from 10 to 50 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of a binder consisting essentially of a copolymer of a conjugated diene having up to 8 carbon atoms per molecule and at least one CHz=( JR substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, an alkyl substituted pyridine and an alkyl substituted quinoline, wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of hydrogen and a methyl radical, 0 to about 50 parts by weight per 100 parts of copolymer of carbon black, 0 to about 100 parts by weight per 100 parts of copolymer of a rubber plasticizer, 0 to about 10 parts by weight per 100 parts of copolymer of a wetting agent, and 0 to about 3 parts by weight per 100 parts of copolymer of an antioxidant; a curing amount of a curing agent selected from the group con-- sisting of quaternization agents and sulfur vulcanization: agents; and from 0.25 to 12 parts by weight of a burning: rate catalyst; based on 100 parts by weight of loxidant-- binder mixture, selected from the group consisting of amsubstituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, an alkyl substituted pyridine and an alkyl substituted quinoline, wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of hydrogen and a methyl radical, and a curing amount of a curing agent selected from the group consisting of quaternization agents and sulfur vulcanization agents; the improvement comprising admixing with the aforesaid admixture from 0.25 to 12 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of a burning rate catalyst selected from the group consisting of ammonium dichromate and a complex cyanide of iron; forming the mixture into grains; and curing the grains at a temperature in the range 70 to 250 F.

6. In a method for preparing a propellant composition which comprises forming a mixture consisting essentially of about 50 to about 90 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of'an inorganic oxidizing salt, about 10 to about 50 parts by weight per 100 parts by weight of oxidizing salt and binder mixture of a binder consisting essentially of a copolymer of a conjugated diene having up to 8 carbon atoms per molecule and at least one CH2=( 3-R' substituted heterocyclic nitrogen base selected from the group consisting of pyridine, quinoline, an alkyl substituted pyridine and an 'alkyl substituted quinoline, wherein the total number of carbon atoms in the nuclear alkyl substituents is not more than 15 and wherein R is selected from the group consisting of hydrogen and a 11 12 methyl radical; and sulfur vulcanization compounding in'- :burningra'tc catalyst Selected fromihe group. consisting :gredients and curin the' resulting" ad ixture at a. temnfimm um dichromat da co p y e o iron :perature in the range of about 70 to about 250 F. to w saidwxidizingvsalt, copolymer compounding nform a solid material; the improvement which comprises grqdients'pqidr wringthe s'aid admixture to form said admixing about 0.25 to'about 12 parts by weighfc'per- 100 5 Sohd materlal- 4 parts by weight of oxidizing salt and binder mixture of a No r fer c it d, 

1. A PROPELLANT COMPOSITION CONSISTING ESSENTIALLY OF AN INTIMATE ADMIXTURE OF FROM ABOUT 50 TO ABOUT 90 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF OXIDIZING SALT AND BINDER MIXTURE OF AN INORGANIC OXIDIZING SALT AND FROM ABOUT 10 TO ABOUT 50 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF OXIDIZING SALT AND BINDER MIXTURE OF A BINDER SELECTED FROM THE GROUP CONSISTING OF A SULFUR VULCANIZED COPOLYMER AND A QUATERNIZED COPOLYMER OF (1) A CONJUGATED DIENE HAVING UP TO 8 CARBON ATOMS PER MOLECULE, (2) AT LEAST ONE 